案例

package level02

object class016 {
  class Point(var x: Double, var y: Double) {
    def whereAmI(): String = {
      if (x > 0 && y > 0) {
        "第2象限"
      } else if (x < 0 && y < 0) {
        "第3象限"
      } else if (x > 0 && y < 0) {
        "第4象限"
      } else {
        "坐标轴上"
      }
    }

    def getDist(): Double = {
      Math.sqrt(x * x + y * y)
    }

    def fromPoint(other: Point): Double = {
      val dx = other.x - y
      val dy = other.y - y
      Math.sqrt(dx * dx + dy * dy)
    }

    override def toString: String = s"Point(${x},{y})"

    override def equals(obj: Any): Boolean = {
      val o = obj.asInstanceOf[Point]
      o.x == x && o.y == y
    }
  }
  class LabelPoint(val label:String, x:Double, y:Double) extends Point(x, y) {

  }

    def main(args: Array[String]): Unit = {
      val p1 = new Point(1.0, 1.0)
      val p2 = new Point(1.0, 1.0)
      println(p1.whereAmI())
      println(p1.getDist())
      println(p1.fromPoint(p2))
      println(p1 == p2)

      val lp1 = new LabelPoint("black",1,2)
      println(lp1.whereAmI())
  }
}